The invention relates to a device for boring spherically curved workpiece inner surfaces.
Such a device is known from German published patent application 30 42 400. This comprises a main body having a slit-shaped through-opening in which a swivel housing is mounted for swivel motion on a tubular axle. The tubular axle lies at a right angle to the axis of rotation of the boring device in order that the cutting tool attached to the swivel housing can move over the entire spherical surface to be machined during rotation of the boring tool. A wedge gearing is provided to enable compensation of cutter tolerances so that the same workpiece internal diameter will be produced. This wedge gearing comprises a wedge longitudinally displaceable in the tubular axle with a ram displaceable at right angles to the axle resting against the wedge. The ram constitutes the connecting member between the wedge and the cutting tool holder which is firmly screwed to the outside of the swivel housing and has a resilient arm on which the actual cutting tool is mounted. By displacing the wedge in the axle, the ram is pushed more or less radially outwardly in order to adjust the trajectory diameter of the cutting tool relative to the axle.
Actuation of the wedge is carried out by a further wedge gearing which is connected to an actuating rod extending through the shank of the boring tool. Since the actuating rod for swiveling the swivel housing extends through the shank of the boring tool in addition to this actuating rod, the known boring tool cannot be readily decoupled from the work spindle. Therefore, it is not suitable for machine tools in which tool changing takes place.
The possibility of the known boring tool to carry out cutter adjustment by an actuating rod inside the tool spindle no longer constitutes an advantage in today's transfer lines To measure the cutter position, the tool has to be brought into a defined rotary position anyway.
A further limitation results from the spring mounting of the arm carrying the actual cutting tool. The stiffness of the spring joint must represent a compromise. To provide as strong a mounting as possible for the cutting tool, the spring joint should be as stiff as possible However, problems then arise with the adjustment for excessively large forces are required for this. For this reason, the designer makes the spring joint only so strong that it is capable of withstanding the forces occurring during the normal cutting operation.
In the case of cutter breakage, the cutting tool holder may become damaged and have to be exchanged. This not only means that the machine is out of action for a certain time, but also involves considerable costs for a new cutting tool holder which has a relatively complicated shape and is correspondingly expensive to manufacture.
Proceeding from this, the object of the invention is to provide a device for boring spherically curved workpiece inner surfaces which is of simple and robust design and is easily exchangeable.